A continuous development of food processing, such as fish products, has taken place in the past decades. A big effort has been put into increasing utilization and value of the product as well as meeting demands for higher throughput and efficiency in processing.
Traditional methods for bone removal include manual trimming fish fillets as well as removal of pin bones. These manual methods are labour intense and time consuming and such processing is giving way in competition to methods based on automated and more efficient processing.
A technology has been developed for searching for bones in fish fillets, analyses, locates and removes the bones with gripping devices, which tears the bones from the fillet. The efficiency of such device, because results of bone removal, has not shown to be satisfactory.
Another disadvantage associated with this technology is that the fish fillets are skinned using traditional skinning devices, which causes deforming of the fillets, gapping occurs making location of pin bones inaccurate as well as increasing the risk of bones moving in the fillet and ending up in locations where the device has a difficulty in finding and locating the bones. The result of this has been manual searching and locating remaining bones using expensive bone scanning device. Such device uses x-ray scanning for locating the bones and a certain group of consumers refuses products that have been treated with x-ray.
Separation of food products, such as fish fillets, chicken fillets, and many others, by using water jet cutting is known in the art. U.S. Pat. No. 4,962,568 discloses how food products are cut to predetermined portion sizes or to predetermined profile shapes, by scanning the items with a camera capable as they move on a conveyor. The camera provides a programmed computer with dimensional data, and utilizes the computer to control the operation of a plurality of high pressure water jet cutters to cut the food products to reduced sizes as dictated by the computer program.
U.S. Pat. No. 5,551,190 discloses an arrangement for fluid jet cutting of food products. The arrangement comprises a movable nozzle which is on a frame. The plant for fluid jet cutting comprises a belt conveyor for moving the products, a device for analyzing the characteristics of the products to be cut, and a device for controlling the operation of the fluid jet arrangement for cutting the products on the conveyor in response to commands from the analyzing device.
Prior art arrangements using water jet cutting are not considered optimal for processes such as removing pin bones from fish fillets, as the back flush from the cutting water beam does interrupt the precise location of pin bones in fillets and the cut in the meat is not sharp enough and close enough to the pin bones. This is because the flesh in traditional state is delicate with soft texture and deforms during cut by the water jet beam. This leads to reduction in yield and value when processing fillets. Moreover, the known water jet arrangements are quite complicated.
Conventional methods including methods using water jet cutting are based on skinning the fillets before bone removal preventing processing valuable products with the skin attached, such as loin pieces or salted flap with skin. Further more traditional skinning causes deforming of the fillets and gapping occurs making location of pin bones inaccurate as well as increasing the risk of movement of bones in the fillet giving problems finding and locating the bones.
U.S. Pat. No. 6,825,446 discloses a technology which can be used for cooling the products, such as fish fillets, to the under-cooled state by using the Combined Blast and Contact cooling method. This gives the necessary precise control of the cooling and an effective cooling for bringing the fillets to the under-cooled state.
Conventional methods are therefore limited to providing skinless products. Conventional methods have a further disadvantage in that the temperature of the product increases during the processing decreasing storage life and quality. These conventional methods have been used until now instead of the manual way of removing pin bones and trimming fish fillets using a complex and expensive devices as well as involving shortage of efficiency to give satisfactory results.